Hi Rob,
Just tried re-ordering it as you suggested, and this was exactly the improvement that I needed. Now getting returns in 0.1 seconds rather than 200+. Much appreciated, Adam ________________________________ From: Rob Vesse <[email protected]> Sent: 15 June 2018 12:12 To: [email protected] Subject: Re: Long response times on TDB queries On 15/06/2018, 11:46, "Adam Ladly" <[email protected]> wrote: 22:18:21 INFO exec :: Reorder/generic ?node <http://example.com/idmapping> ?id ?node ?p "http://www.ncbi.nlm.nih.gov/gene/1956"; So it looks like TDB is using a generic execution ordering and for your data this is clearly sub-optimal, I suspect you have far more triples matching the first pattern than the second. Firstly I would try using { } to rewrite your query and explicitly force the execution order i.e. PREFIX els: <http://example.com/> SELECT DISTINCT ?id FROM <urn:x-arq:UnionGraph> WHERE { { ?node ?p "http://www.ncbi.nlm.nih.gov/gene/1956"; } ?node els:idmapping ?id . } Although the optimiser might flatten that into a single BGP anyway in which case you might still have the same problem. Secondly I would try generating a stats.opt file per the documentation - http://jena.apache.org/documentation/tdb/optimizer.html#generating-a-statistics-file Once you have this copy it to stats.opt in your database directory (per the documentation don't try and generate directly to this location) and then retry your original query. You should then hopefully see Reorder/stats being used which if your data is structured as I suspect the statistics should reverse the order of your triple patterns leading to faster execution Hope this Helps, Rob
